When a pigment is incorporated into various aqueous resin compositions, such as aqueous resin coating compounds, a dispersing agent for a pigment is generally used. Commonly employed dispersing agents for pigments include polyelectrolytes, e.g., polyphosphates, e.g., sodium tripolyphosphate, sodium tetraphosphate, and sodium hexametaphosphate; a sodium alkylnaphthalenesulfonate-formalin condensation product; low-molecular ammonium polyacrylate; and a low-molecular ammonium styrene-maleate copolymer.
These pigments dispering agents are necessary to assist deflocculation and dispersion of the pigment, to reduce the viscosity of a pigment paste, as well as to prevent agglomeration of the pigment particles. However, where a pigment dispersing agent is added in an amount sufficient for obtaining desirable dispersibility, the dry film of the resulting pigment dispersion has reduced water resistance or weather resistance.